This invention relates to improvements in a method for strengthening a surface of a metal member having a carbon-based film, in order to form a structure containing fine grains at the surface of the film-coated metal member thereby highly increase mechanical strength, wear resistance and the like.
In a metal member such as a machine part and the like, it is required to increase mechanical strength and wear resistance at a surface of a metal product or the metal member in accordance with design specifications of the metal product. Hence, conventional techniques have met the above requirement by making a heat treatment such as quenching, carburizing and nitriding on the metal member or by making a shot peening on the surface of the metal product, as disclosed in Japanese Patent Publication No. 3212433.